Combustion chamber for internalcombustion engines



R. P. PESCARA 2,580,951

Jan. 1, 1952 COMBUSTION CHAMBER FOR INTERNAL-COMBUSTION ENGINESv .Illu-Ill .l'li

File'd Dec. 19, 1947 INVENTUR RAUL PnTERas Pescnna ATTORNEYS Patented Jan. I, 1952 .3.

fumrso STATES PATENT [OFFICE COMBUSTION. CHAMBERFORINTERNAM COMBUSTION ENGINES Raul Pateras Fescara,0ap dAntib-cs, Fran-co AppIicationDecember 19, 1947, SeriaLNo-792,534

In Frances'eptember, 20,1947

2.Claims. (Cl. 1 23-1 91 Thepresent invention relatesto internal comis high: and permits of obtaining a substantial bustion engines and more parti'cuiatlybut not cooling, of the gaseous contents of zone whereexcl'usively, gasoline'eng-ines; 4 I as the Ot'hGFZOIlB'B- which is-located' opposite Its chief cbjectis to provide amengine of this the exhaustva-lve orvalves 4, isof greaterheight type whichis-better adapted to meet the-req'uire-- 5 andvolu-me-than the-first zoneand consequently merits of practice than those used up to this time. constitutes a hot zone.

Preferred embodiments-of my invention will be Furthermore; and also according'tothemain hereinafter describedwith reference to the acfeature of my invention, the spark plug, theseat companyingdrawings, given merelyby way 01? of which isindicated'at 6 in the drawings, is example-and in which-r 10 mounted int-he hottest portion of the second Fig. 1- shows, in axial section, the portion of mentioned zone on the side-opposed tothe inlet a four stroke engine cylinder headadjacent to valve; ignition preferably taking-place with a-conthecombusti'on chamber and the-upper portion of siderable lead the piston thereon-said: engine being made ac- Finally, the ratio ofthe volumes of the hot cording-to the-invention; zone and the cold zone i's-advantageously chosen- Figt 2isa section on-the lineII-II ofF-ig. 1 higherthani thehot zonegenera-llyconstituting Fig. 3- is a section-analogous to that of Fig. 2- at least 60 of the total'vol'ume of thecom-busof a modification; tionchamber;

Finally, Fig. 4 diagrammatically shows the With the above'statedconstructional arrangepropagation of combustion in: the combustion merits, thefuel being an ordinary gasoline havchamber-of an engine-made according to my ining'an octane number of for instance approx-ivention. mately- 60'; and the walls of the-combustion cham- It is-know-nthat the eflicieney of an engine is her constituted by cast iron, and if ignition takes the higher as-the rate oi compression is higher. placewi-tha leadgreaterthan 4.0 (for instance However, increases in therateof'compressionare- 2-5 equal to 44 for a-cast iron cylinder head) withlimit d. by: th appearance of the phenomenona number of revolutions per minute-of the enknown under the'name of detonation. gine of about 3000, I can obtain a rate of com- The rate of compression-abovewh-ich-thisdetopression of the fuel mixture of 7.5 and even 8 nation phenomenon appearsdepends essentially without detonation taking place. 0n the con-- upon the-natureof the fuel that isused; tor m trary, flame propagation is slowed down by the stance, uptomour, to-avoid detonation, i t was not throttledsectionor the combustion chamber;

possible, in engines intended to utilize ordinary 9f course,- such a combustion chamber'can be gasoline, iorinstance. of an octane number equal obtained in many ways.

to 60,: to exceed a rateof compression of: B, with Figs. 1 and 2 show an advantageous embed-L cast iron walls for limiting-the combustion chain ment of such a chamber. The end wall of piston her, the cylinder. diameter; being, for instance, i is given an unsymmetrical-shapesoas to have,

equaltoflflmm. opposite the inlet valve 3 housedin aninclined In order to utilize higher rates of compression portion of the inner-surface-of the cylinder'head, it was necessary; upto the present time, to make -proj'ection 1 t an inclinedsurfac 1" use oi s eci easeli es ha i a hi h oc a 40 alle'l' to said inner surface inclined portion, the number- A cold zone 5" of the combustion chamber being The main .features of the present invention thugformed between/the urfac ofproi'ection permits of increasing, for a given fuel, the rate 1 of the t and n t innr surface of compression by at least one unit and generally of valve 3'; from oneand ahali to twounit$withoutchangh r i I v me, the. matter that. constitutes; the walls or, the a fig i ffi fifiifi fifi i fif ifii 9 b not diameter of latter being locatedin a portionof'the. inner Wall, 3 cylmderrby gwmgtha i i of' the cylinder head that is perpendicular to, the. iandthecylmder headzoithe engine cylmderaxis of thejengme cylinder the zone between this whrchcylmder headv includes in. its upper: wall necerss and the exhaustvawe being of a gmat at least one inlet valve..3 andonelexhaust valve height and its vorume being more than one haunt a shape such that the combustion chamber, thetotal vamme of the combustion chamber limited between theend'wallofi piston I and the This Second mentioned. e e' z inner surface of cylinder head 2, includes two (if-the mb th th zones one of which, zone 5, located opposite in- CO 1118 on ,9 am er Smce' elem" let valve 3 the head of which forms an essential m 0 portion of the walls of this zone, isof small height, that is tosay is. fia ,.whereby hi. this zone. the ratio area volume.

volume is much lower than the same ratio in the first most of the residuary gases are expelled through the exhaust zone and improve cooling and volumetric efficien'cy since heating and expansion of the gaseous mixture are ;reduced due to the fact that the amount of residuary exhaust gases is much smaller.

, It is possible iurther to improve the turbulence created inside the combustion chamber by giving the cylinder head and the piston end wall a shape analogous to that shown by Fig. 3; according to this modification the cylinder head and the projection of the piston end wall are given, in a plane at right angles to the plane in which are located the axes of the inlet valve 3 and exhaust valve 4, a width smaller than the diameter of the engine cylinder. I thus create, at the end of the inward stroke of the corresponding piston, supplementary turbulences T1 and T2 which are added to the above mentioned turbulence T.

Concerning the location of the spark plug at the opposite of the inlet valve and in the hottest portion of zone 5", it ensures a propagation of combustion as diagrammatically shown by Fig. 4, in which the spark plug is designated by 6a, whereas the oval area indicated by this figure represents the interval volume of the combustion chamber seen in plan view and the curves present inside said area represent the different positions of the flame front as it is travelling.

Combustion seems to take place in the following manner; I

When the spark is produced, the beginning of combustion is extremely quick, due to the high temperature and perfecthomogeneity and gasification of the fuel mixture. But, contrary to what takes place in most of thecombustion chambers where propagation of the flame front is uncontrolled and consequently propagation velocities capable of producing detonation are quickly reached, combustion, first highly accelerated when propagating through the hot zone, is gradually slowed down when reaching the cold zone to a relatively low rate (Fig. 4), consequently avoiding detonation. The immediate consequence of flame front propagation control is to eliminate,

whatever be the rate of compression, anyhardness of operation as generally takes place when the flame propagation velocity reaches values close to detonation velocities.

Besides, the fact that it is necessary to utilize,-

according to the invention, a very important lead to ignition (for a gasoline having an octane number of and for 3000 revolutions per minute, the best lead in a cast iron cylinder head is equal to about 44 degrees) corroborates the above stated hypothesis of a combustion which is first quick but gradually slowed down.

Of course the invention is applicable to engines having any number of cylinders;'in an engine having a plurality of cylinders in line, the axes of the inlet valves 3 and exhaust valves 4 should be disposed in a plane perpendicular to the longitudinal axis of the engine.

In a general manner, while I have, in the above description, disclosed what I deem to be practical and efiicient embodiments of my invention, it should be well understood that ,I do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the'present invention as comprehended within the scope of the accompanying claims.

What I claim is:

1. In an internal combustion engine, the ,combination of a cylinder, a piston movable in said cylinder, a cylinder head carried by said cylinder, only one inlet valve and one exhaust valve having their centers disposed at respective points of the upper wall of said cylinder head located in acommonaxial plane of the cylinder on opposite sides of the longitudinal axis of said cylinder, the portion of said cylinder head inner wall in which is provided the inlet valve being oblique to said longitudlnal axis and the portion of said inner wall in which is provided the exhaust valve being at right angles to said axis and adjoining said first mentioned portion and the sum of the diameters of said two valves being nearly equal to the dimension of said inner wall in the plane of said centers, the portion or the piston end face located opposite said intake valve pro ecting toward said cylinder head and being parallel to the corresponding portion of said cylinder head inner wall at a small distance thererrom, whereas the remainder of said piston end face is concave. so as to form between said cylinder head inner wall and said piston end face a combustion chamber made or two zones, one of which, located opposite said inlet valve, is flat and the other is or relatively substantial thickness, and a spark plug carried by said cylinder head in the second mentioned zone of said combustion chamber in the axial plane of said valves, said engine being operaole without detonation at a compression ratio of at least substantially 7.5.

2. A-comolnatlon according to claim 1 in which the cross section or the inner wall or said cylinder head in the transverse plane along which it is mounted on said cylinder is narrower, in a direction at right angles to the axial plane of the valves,- than the cross section of the cylinder in the same transverse plane, said piston projecting beyond said transverse plane into said cylinder head to create a supplementary turbulence.

RAUL PATERAS PESCARA.

REFERENCES CITED The following references are of record in the file of this patent:

" UNITED STATES PATENTS OTHER REFERENCES Automobile Engineer," February- 1940, PP. 

